1. Field of the Invention
The present invention relates to a phosphate gel for passivation, which is used to remove corrosion, caused by welding, from the pipelines, towers, valves and the like of structures installed in ships, manufactured in shipyards, or large-sized engines, manufactured in heavy industrial companies, and to form a phosphate coating film on the pipelines and the like.
2. Background of the Related Art
Forming layers of metal compounds by causing chemical changes (oxidation, reduction, substitution, alloying, etc.) on metal surfaces is referred to as chemical coating, the most typical of which is phosphate coating. Phosphate coating refers to making on metal a new, non-metallic and non-conductive surface. That is, phosphate coating refers to making an inorganic crystal or an amorphous coating film on metals, such as steel, aluminum, zinc, cadmium, or alloys thereof, and is also called “Parkerizing” or Bonderizing” (Amchem Products, Inc., USA). Also, the phosphate coating, which is carried out using a simple method and equipment, incurs low production cost and is economical. Prior patents relating to the formation of phosphate coatings are as follows: Korean Patent Registration No. 1984-0005227, entitled “Phosphating agent for use at room temperature and use thereof”; Korean Patent Registration No. 10-0324089, entitled “Method for forming phosphate-based coating on metal surface”; Korean Patent Registration No. 10-0397049, entitled “Method and apparatus for forming phosphate coating on steel wire”; and Korean Patent Registration No. 10-0536884, entitled “Zinc-calcium-based phosphate coating/coloring agent and method of forming phosphate coating using the same”. In said patents, a dipping process is carried out in the liquid phase. Also, Korean Patent Registration No. 10-0491178, entitled “Electro-phosphate coating method”, and Korean Patent Registration No. 10-0554895, entitled “Phosphate coating system and chemical coating system”, employ electrolysis. As described above, phosphatizing agents, which are currently used in the industrial field, are in the liquid phase and do not employ gel-type phosphate.